A seal for use between a shaft rotatable about and extending along an axis and a housing through which the shaft passes axially typically has a rub ring fixed on the shaft outer surface and having an outer surface centered on the axis and a flexible seal ring formed with an outer portion fixed in the housing, an inner lip engaging radially inward against the outer rub-ring surface, an intermediate portion extending radially inward from the outer portion, and a relatively thin and flexible annular web connecting the lip to the intermediate portion. An inner protector ring is fixed in the seal ring and has a radially inwardly projecting inner flange juxtaposed with the rub ring and spaced radially outward from one of the outer surfaces. An outer protector ring is fixed in the seal ring and has a radially in wardly projecting inner flange juxtaposed with the rub ring and spaced radially outward from one of the outer surfaces.
Such shaft seals are known from EP 91,983, British 590,874, and British 879,503. In such a seal the flexible lip of the seal ring is thus protected by the normally metallic inner and outer protector rings so that foreign matter, in particular dust and particulate material, cannot get to this part of the seal. They also protect this flexible lip during installation of the shaft seal.
Thus the inner and outer protector rings act as a sort of housing that wholly encloses the seal ring, in particular covering its entire outer periphery. The result is that the shaft seal is fairly bulky, in fact much larger than the seal ring which is all that is really doing any work when the seal is installed. Furthermore the inner and outer protector rings frequently form a leak-prone gap with the shaft outer surface and the ends of the rub ring, so that a path is left open for foreign particles to get into the seal.